The Liquid Crystal Display (LCD) is one of the most widely utilized flat panel displays, and the liquid crystal display panel is the core component of the Liquid Crystal Display. The liquid crystal display panel generally comprises a Thin Film Transistor Array Substrate (TFT Array Substrate), a Color Filter (CF) and a Liquid Crystal Layer arranged between the two substrates. In general, the array substrate and the color filter substrate comprise pixel electrodes and common electrodes. As the voltages are applied to the pixel electrodes and the common electrodes, the electrical field can be generated in the liquid crystal layer to twist the liquid crystal molecules in the liquid crystal layer, and then to adjust the polarization of the light incident into the liquid crystal layer for making the liquid crystal display panel show images.
The Vertical Alignment (VA) liquid crystal display panel possesses extremely high contrast than the liquid crystal displays of other types. It has very wide application in large scale display, such as television or etc. The pixel electrode inside the VA type liquid crystal display panel is generally designed to be a pozidriv structure: the vertical trunk and the horizontal trunk of the pixel electrode are perpendicular to equally split the area of the pixel electrode into 4 domains, and each region is composed with spread strip branches appearing ±45°, ±135° angles with the vertical trunk or the horizontal trunk. In such pozidriv pixel electrode structure, because the included angles of the slit with the vertical trunk and the horizontal trunk in each pixel electrode domain are the same, a certain visual color difference or visual color deviation must exist at large view angle.
At present, for improving the large view angle color washout phenomenon of the VA type liquid crystal display panel, the Low Color Shift (LCS) design is executed to the pixel units, which is to divide each sub pixel into a main region and a sub region. One independent main region pixel electrode is positioned in the main region, and one independent sub region pixel electrode is positioned in the sub region. Both the main region pixel electrode and the sub region pixel electrode utilize the pozidriv structure design. In the display process, the same data signal voltage is applied to the main region pixel electrode in the main region and the sub region pixel electrode in the sub region, and then, the voltage of the sub region pixel electrode is pulled down so that the voltage level of the sub region pixel electrode is lower than the voltage level of the main region pixel electrode. Such solution makes the twist angles of the liquid crystal molecules in the main region and in the sub region are different, and thus to improve the large view angle color washout phenomenon of the VA type liquid crystal display panel.
However, after utilizing the aforesaid LCS design to the pixel unit, the region between the main region and the sub region of the sub pixel are opaque, and the aperture ratio and the transmission rate of the liquid crystal display panel are decreased.
For reducing the impact to the transmission rate while improving the large view angle color washout, a design solution of the pixel unit structure is proposed, which includes a red sub pixel, a green sub pixel and a blue sub pixel, the sub pixels of three various colors, wherein the green sub pixel with the highest transmission rate is an integrated structure without the main region, sub region division for raising the entire transmission rate of the liquid crystal display panel, and at least one of the red sub pixel and the blue sub pixel is divided into a main region and a sub region for improving the large view angle color washout.
However, it is discovered in the practical display experiment, the aforesaid pixel unit structure remains having issues. The actual electrical properties of the red or blue sub pixel divided into the main region and the sub region have inconsistent situations with the influence of the liquid crystal display panel design, the feed-through voltage in the panel and the other capacitor coupling. Under the circumstance that the common voltage are the same and the inputted data signal voltages are the same in the liquid crystal display panel, because the red or blue sub pixel is divided into two parts, the actual data signal voltages of the red or blue sub pixel divided into the main region and the sub region are different from the actual data signal voltage of the green sub pixel having the integrated structure. Along the different areas along the horizontal direction in the panel, the common voltage actually is not at the symmetric center position of the data signal voltage in the positive polarity driving cycle and the data signal voltage in the negative polarity driving cycle of the red or blue sub pixel. Thus, it results in showing the different effects. The brightness of the red or blue sub pixel drifts, and significantly influences the color uniformity of the entire liquid crystal display panel in the gray scale image.
FIG. 1 shows an illustration of the aforesaid pixel unit structure. Both the green sub pixel 20 and the red sub pixel 10 utilize the integrated structures, and only the blue sub pixel 30 is divided into a main region 301 and a sub region 302. FIG. 2 is a relationship diagram of an actual data signal voltage and a common voltage VCOM in the left, middle and right, three different areas of the liquid crystal display panel as regarding the illustration of FIG. 1. The V+ represents the data signal voltage in the positive polarity driving cycle, and the V− represents the data signal voltage in the negative polarity driving cycle, and the common voltage VCOM of different areas are the same values. The fine dotted line represents the data signal voltage of the green sub pixel, and the thick dotted line represents the data signal voltage of the blue sub pixel. Accordingly, the blue sub pixels have color deviation at the left side, the right side of the panel, and the bad conditions of blue deviation in the left, the green deviation in the right and the more obvious flicker happen.
Most liquid crystal display panel according to prior art do not utilize the design that various common voltages VCOM are set for the various regions of the panel. Therefore, for the sub pixels divided into the main region and the sub region, such as the blue sub pixels, the common voltage VCOM always has asymmetry.